1. Technical Field of the Invention
The present invention relates to an imaging apparatus capable of acquiring a plurality of types of images produced based on a plurality of wavelength bands of light, and an optical filter and an image processor which can be employed by the imaging apparatus.
2. Related Art
In the technical field above, a conventional image processing apparatus, which is disclosed by Japanese Patent Laid-open Publication No. 2006-325135, for example, is known. This publication teaches a technique of processing one type of acquired images using a plurality of processing techniques, which thus produces a plurality of types of images whose optical characteristics are different from each other. The plurality of types of images are telephotographic images and wide field-of-view images, for example.
By the way, in terms of raising detection accuracy of objects, some teachings are known. For example, when detecting objects such as pedestrians and vehicles from images acquired at night, images acquired using light of a wavelength band including that of infrared light but excluding visible light of a short wavelength, which images are referred to as a first acquired image, may improve detection accuracy for the objects. Meanwhile, when detecting objects such as edges of white lines on the road (i.e., different illuminate regions in acquired images) from images acquired at night, images acquired using light of a wavelength band including visible light of a short wavelength, which images are referred to a second acquired image, may improve detection accuracy for the objects.
However, it is impossible for the conventional imaging processing apparatus, as disclosed by the foregoing patent application, to control the optical characteristics of light producing images to be captured, because the conventional imaging apparatus performs only fixed processing on the acquired images. Hence, if the first and second acquired images are acquired, two types of imaging means for both the first and second acquired images should be prepared separately.
Meanwhile, as a technique of acquiring the first and second acquired images, there has been known another one. Practically, there is known an imaging unit provided with imaging elements serving as effective pixels, half of which pixels are made to capture pixel signals for the first acquired image and the rest half are made to capture pixel signals for the second acquired image. This way of use the pixels, half-by-half division way, allows one imaging unit (i.e., camera) to be used for acquiring both the first and second acquired images. However, due to a decrease in the number of effective pixels for each acquired image, this division way may decrease imaging sensitivity and decrease resolution in detecting edges of objects.